ArcGISImageServiceLayer Time Error

Question

When I use an image service in mxml like so:
<esri:ArcGISImageServiceLayer id="esriImageLayer" imageFormat="png8" visible="false"
           url="http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/World/MODIS/ImageServer"/>

everything works OK with the layer and timeSlider.  When I create the layer in actionscript:
var lyr:ArcGISImageServiceLayer = new ArcGISImageServiceLayer("http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/World/MODIS/ImageServer");
lyr.imageFormat = "png8";
lyr.visible = true;
timeSlider.createTimeStopsByTimeInterval(lyr.timeInfo.timeExtent, 1, TimeInfo.UNIT_MONTHS);
timeSlider.visible = true;

I get an error on the createTimeStopsByTimeInterval line:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

Any idea as to what I'm missing here?

Thanks,
Glen

GWReid · Answer

Thanks Ivan, that was the issue.

IvanBespalov · Answer

lyr.timeInfo is NULL

Because layer is not loaded yet.

1 - Add layer to map:map.addLayer(lyr);

or dispatch Layer load event (if you do not want to add layer to your map)lyr.dispatchEvent(new LayerEvent(LayerEvent.LOAD, lyr));

2 - listen LayerEvent:lyr.addEventListener(LayerEvent.LOAD, onLayerLoad, false, 0, true);
lyr.addEventListener(LayerEvent.LOAD_ERROR, onLayerLoadError, false, 0, true);

protected function onLayerLoad(event:LayerEvent):void
{
    //get lyr.timeInfo here
}

protected function onLayerLoadError(event:LayerEvent):void
{
    //trace error
}